Digital modem technology using a multi-carrier method such as orthogonal frequency division multiplexing (OFDM) should use complicated reception terminal synchronization technology for precise signal synchronization, a high-priced amplifier having a linear characteristic, and high-priced analog-to-digital (AD)/digital-to-analog (DA) converters having high resolution. Meanwhile, since digital modem technology using a single-carrier method uses simple reception terminal synchronization technology, a low-priced amplifier, and AD/DA converters having low resolution, can easily realize a low power/low-priced receiver having a simple structure. Since the advantage of the single carrier method is applied to low speed communication using a low-order quadrature amplitude modulation (QAM) or phase shift keying (PSK), the single carrier method is applied to mobile phone service using code division multiple access (CDMA).
In case of high communication using QAM signals of high order of 32-QAM or more, influences by a signal noise, channel distortion, and carrier synchronization reduce receiver performance. Particularly, in the case where wireless communication is performed in an indoor space, a variety of multi-path fading is generated due to complicated indoor environments to aggravate the channel distortion of received signals. Accordingly, conventional signal carrier receiver algorithm and structure cannot be used for a modem system for high speed indoor communication.
To overcome limitations of the multi-carrier method, single-carrier frequency domain equalization (SC-FDE) has been proposed recently. In SC-FDE, a transmission terminal converts signals into a block using a cyclic prefix and transmits the same as in OFDM, and a reception terminal converts signals into signals in a frequency domain to perform channel equalization.
The limitations of OFDM can be overcome using SC-FDE, but fast Fourier transform (FFT) and inverse fast Fourier transform (IFET) should be performed at the reception terminal, which makes the structure of a corresponding receiver complicated. Therefore, SC-FDE is not suited for wireless personal area network (WPAN) pursuing a simple receiver structure and low power consumption.